Cab tilt hydraulic circuit

ABSTRACT

A control system for use with a truck having a tilt type cab wherein the cab is tilted by means of hydraulic pressure. The system includes a hydraulically operated latch mechanism such that the operator may unlatch the cab and raise it using the same control mechanism. The system also includes a secondary control means which will override the first control means with respect to the latch structure enabling the operator to latch the cab in position such that it may not be raised by the first control means.

1 51 3,706,470 Dec. 19, 1972 United States Patent Johnson 2,740,4874/1956 Murty et al.............................l8()/89 [54] CAB TILTHYDRAULIC CIRCUIT [72] Inventor: Robert E. Johnson, Kent, Wash.

Primary Examiner-Leo Friaglia Assistant Examiner.lohn A. PekarAttorney-Seed, Berry & Dowrey Assignee:

Pacific Car and Foundry Company, Bellevue, Wash.

July 23, 1970 Appl. No.: 57,503

[57] ABSTRACT A control system for use with a truck having a tilt type[22] Filed:

cab wherein the cab is tilted by means of hydraulic pressure. The systemincludes a hydraulically operated latch mechanism such that the operatormay unlatch [52] US. C, 180/89 [51]Int.Cl..............................................B62d 33/06 .296/28C; .180/89; 298/38 the cab and raise it using the same controlmechanism.

[58] Field of Search..........

The system also includes a secondary control means which will overridethe first control means with [56] References Cited respect to the latchstructure enabling the operator to UNITED STATES PATENTS latch the cabin position such that it may not be raised by the first control means.

3,472,547 10/1969 London..................................l80/892,749,175 .298/38 6/1956 King et al. 6 Claims, 2 Drawing FiguresPATE'N'TEDHEE 19 m2 INVENTOR. ROBERT E. JOHNSON ATTORNEYS CAB TILTHYDRAULIC CIRCUIT BACKGROUND OF THE INVENTION In the cab-over-engine ortilting-cab type truck, the cab is pivotally secured to the vehicleframe at the front end of the cab so that when the cab is tiltedforwardly the engine and accessories are exposed for convenientservicing and repairs. The invention is concerned with a locking meansin combination with the lifting means, the first for locking the cabto-the vehicle frame when the cab is in a closed position over theengine. and the lifting means for moving the cab from the closed, to theopen position and supporting it during work upon the engine. The liftingmeans and the locking means are interrelated so that the operator mayconveniently release the cab structure and lift said structuresimultaneously using the same control mechanism.

It is an object of the present invention to provide a tilt cab structurehaving a hydraulic system wherein the same fluid source is used for bothraising and lowering the cab as well as for unlatching the cabstructure, enabling it to be raised, said unlatching function beingsubject to lockable overriding controls.

Another object of the present invention is to provide a latching andlifting structure for cab-over type trucks wherein the same controlmechanism is used for unlatching the structure and lifting the cab.

Yet another object of the present invention is to provide a controlsystem for a cab-over truck wherein the same circuit and pressure sourceis used for raising the cab and unlatching the cab, but furtherincluding a secondary control means which overrides the lifting controlmeans. The secondary control means is operably connected to the latchstructure enabling the operator to lock the cab in a closed positionpreventing raising of the cab.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic environmentalview showing the relationship of the mechanism in the preferredembodiment;

FIG. 2 is a hydraulic circuit diagram of a control mechanism for theinventive structure.

DETAILED DESCRIPTION OF THE DRAWINGS As seen in FIG. 1 the inventivehydraulic circuitis designed to be used upon a cab-over vehicle havingwheels 2, frame structure 4, and a cab 6 having a drivers compartment 8.The drivers compartment includes the conventional seat, steering wheeland operating instruments.

Secured to-the forward portion of the cab, inside the shell, are a pairof telescoping cylinders 10 and 12 which are likewise secured to theframework, said cylinders providing a lifting force for tilting the cabduring work upon the components such as the engine and cooling system,which are located beneath the cab construction. Mounted on theframestructure and accessible from the outside, the cab is a pumpcontrol means 14 for supplying hydraulic fluid to the cylinders 10 and12 for raising the cab structure 6. Located upon the side of the pumphousing is a handle 16 for actuating the pump and directing the pressurenecessary for expanding the cylinders and raising the cab 6. Mounted tothe rear portion of the cab and adapted to cooperate 3063 T200 Mi -3i)!with a structure mounted to the frame is a hydraulically operated latchmechanism 18 which may be similar to that disclosed in U.S. Pat. No.3,497,257, issued Feb. 24, 1970 to Mr. l-Iirst. There is sufficientpiping to connect the hydraulic pump-tothetelescoping cylinders 10 and12 and to manually operated hydraulic control valve 20 and to the latchmechanism 18. The valve 20 is located in the cab 6 as illustrated inFIG. 1. described with reference to FIG. 2 which includes a schematicrepresentation of the various elements hereinabove described. Asv seenin FIG. 2, the control valve 20 has two positions: locked, which is theopen position of the valve, and unlocked, which 'would be the closedposition of the valve in the preferred embodiment. The circuit will nowbe described with the valve in its locked or open position. The operatorwill start the pump 14 by moving the handle 16 to the. appropriateposition, fluid will be circulated through lines 22, 24 and 28 tovthe.cylinders 10 and 12 where pressure will be placed upon the pistonswithing the cylinders 10 and 12 where pressure will be placed upon the.pistons within the cylinders attempting to open the cab. In thiscondition, i.e., locked, the latch mechanism 18 will be secured to theframework preventing the cab from tilting. As notedabove, the latchstill is locked, preventing thecab from tilting, and the fluid underpressure will leave junction point 26 via line 30 proceeding to junctionpoint 32. An increase in fluid pressure in .line' 34 would unlatch thecab. However, since the, valve 20 is in its locked or open condition,the fluid will circulate without impedance through line 36 passingimmediately through valve 20 through line 38 and 42 to the other ends ofdouble acting cylinders 10 and 12..The fluid passes through junctionpoint 40 and then through line 44 back to the reservoir (not shown). Thefluid will continuev to circulate as noted above without impedance. Insummary, it can be seen that when the valve 20 is in its locked or openposition, the fluid will be pumped through lines 22, 24, 30, 36, 38 and44 back to the pump without activating-any of the elements.

When the operator wishes to lift a cab for maintenance purpose, he willmove the valve 20. to the unlocked position, which is the closedposition of the valve. The operator then activatesthe pump and fluidunderpressure. entering line 22 passes through line 24 and line 30 butwill not be allowed to pass through valve 20. The resultant pressure inline 34 will unlatch the latch 18. Latch l8 requiring less operatingpressure than cylinders 10 and 12 disengagesalmost immediately. When thelatch l8 is disengaged, the pistons within the double acting cylinders10 and 12 can move when sufficient pressure is achieved and will thusraise the cab.

When the operator wishes to lower the cab, he will move the handle 16 tothe. appropriate position allowing all of the fluidv to leave the linesand go into the reservoir allowing the cab to slowly return to itslowered position at which point the spring activated latch will securethe cab position.

It can thus beseen that with the additional valve control 20 locatedwithin the cab of the vehicle, that once the vehicle doors are locked,it is impossible to raise the cab structure for purposes of vandalism orthe like.

- With the valve in the locked or open position, the pump will simplycirculate the fluid through the system l060ll without damage. In theevent that the latch were forced, an attempt to raise the cabhydraulically would nected with a conduit interconnecting the latchmeans,

the lift means and the control .means, said o've-ride means allowingfluid pumped to the lift means and the latch means to circulate freely,not causing latch disengagement orliftactuation whereby the remoteoverride means may be utilized, preventing unauthorized tilting of thecab.

2. A latch mechanism 7 as in claim 1 wherein the remote override meansis located within the cab of the truck.

3. A hydraulic control circuit for use with a truck ineluding a mainframe and 'an enclose d operators cab utilizing a hydraulic lift for atilt cab comprising: a source of fluid under pressure, latch means forselectively latching the cab to the frame, hydraulic ram means mountedbetween the cab and the framework to lift one edge of the cab from theframework permitting access to mechanism thereunder, conduit meansinterconnecting the source of fluid under pressure with the ram and thelatch, control means interconnected with the conduit means for directingfluid under pressure simultaneously to the latch means and the ram meanssaid latch requiring less pressure to operate assuring an unlatch of thecab prior to actuation of the ram to raise the cab, override meansmounted within the cab and interconnected with the conduit meansoperable to selectively permit or to prevent pressure buildup within thecircuit whereby when the cab is locked and the override means is placedin the locked or open condition it is impossible to raise the cab.

4. A circuit as in claim 3 wherein the overridemeans comprises ahydraulic valve which, when in the open or locked condition, allows freeflow of the fluid from the pressure source through the conduits and backto the source without significant pressure buildup within the system.

5. A circuit as in claim 3 wherein the control means is mountedexteriorly of the cab and allows control of thehydraulic ram means fromoutside the cab when the override means is in its closed or unlockedcondition.

6. A circuit as in claim 3 wherein the latch means, the hydraulic rammeans, and the override means are all operatively interconnected with aclosed circuit connected with the source of fluid under pressure suchthat opening of the override means disables the latch means and the rammeans by allowing free flow of fluid and preventing tilt of the cab.

=k I I!

1. A remote control latch mechanism for a tilt-type cab comprising; ahydraulically operated Latch, hydraulic lift means for tilting the cab,fluid control means for simultaneously disengaging said latch andlifting said cab, and remote override means functionally interconnectedwith a conduit interconnecting the latch means, the lift means and thecontrol means, said overide means allowing fluid pumped to the liftmeans and the latch means to circulate freely, not causing latchdisengagement or lift actuation whereby the remote override means may beutilized, preventing unauthorized tilting of the cab.
 2. A latchmechanism as in claim 1 wherein the remote override means is locatedwithin the cab of the truck.
 3. A hydraulic control circuit for use witha truck including a main frame and an enclosed operator''s cab utilizinga hydraulic lift for a tilt cab comprising: a source of fluid underpressure, latch means for selectively latching the cab to the frame,hydraulic ram means mounted between the cab and the framework to liftone edge of the cab from the framework permitting access to mechanismthereunder, conduit means interconnecting the source of fluid underpressure with the ram and the latch, control means interconnected withthe conduit means for directing fluid under pressure simultaneously tothe latch means and the ram means said latch requiring less pressure tooperate assuring an unlatch of the cab prior to actuation of the ram toraise the cab, override means mounted within the cab and interconnectedwith the conduit means operable to selectively permit or to preventpressure buildup within the circuit whereby when the cab is locked andthe override means is placed in the locked or open condition it isimpossible to raise the cab.
 4. A circuit as in claim 3 wherein theoverride means comprises a hydraulic valve which, when in the open orlocked condition, allows free flow of the fluid from the pressure sourcethrough the conduits and back to the source without significant pressurebuildup within the system.
 5. A circuit as in claim 3 wherein thecontrol means is mounted exteriorly of the cab and allows control of thehydraulic ram means from outside the cab when the override means is inits closed or unlocked condition.
 6. A circuit as in claim 3 wherein thelatch means, the hydraulic ram means, and the override means are alloperatively interconnected with a closed circuit connected with thesource of fluid under pressure such that opening of the override meansdisables the latch means and the ram means by allowing free flow offluid and preventing tilt of the cab.